“Blondes make the best victims,” Alfred Hitchcock once said. “They’re like virgin snow that shows up the bloody footprints.”

So begins The Girl, HBO’s deeply (and rightly) gnarly exploration of the fraught relationship between Hitchcock and arguably the most legendary of his blonde ingénues, Tippi Hedren (Sienna Miller).

Having happened upon the lovely Hedren in a TV commercial, “Hitch” (Toby Jones, best known for voicing beloved house-elf Dobby in the Harry Potter series) immediately starts grooming the then-unknown model to star in The Birds, his much-anticipated follow-up to Psycho. (He hints that Hedren was originally a less-than-desirable replacement for Grace Kelly, who had recently married and thereby fallen out of favor in the Hitchcock camp.)

It’s the star-making role of a lifetime, and Tippi is deeply grateful: “I’ll be putty in your hands!” she promises. Soon, Hitch is art-directing everything from her lipstick to her off-camera wardrobe, and by the time she accepts a starring role in his next film, Marnie, Tippi’s polite side-stepping of his sexual aggression is rewarded with unwelcome gropes, straight-up threats, and on-set endangerment. A scene where Hitchcock subjects Hedren to forty-plus takes of being attacked by live birds is particularly cringe-inducing.

It’s a gripping film, but only because it’s based in such shocking reality. Hitch’s unredeemable grossness squashes the plot. Sure, he gets drunk and does the inevitable wah-wah-this-is-why-I’m-the-way-I-am schtick that usually signifies growth and change, but mere minutes later, he locks Hedren into his office and demands that she owes him sexual favors. Both Hedren and Hitchcock’s assistant director Jim Brown (played by the sweet-as-pie Carl Beukes), have criticized the director for misogynist stunts like these—but just because it’s authentic doesn’t mean it makes a good narrative. Completely unsympathetic characters aren’t fun to watch, and nor is the silent suffering of those they torture.

Though it’s not a wet-your-pants thriller, The Girl isworth seeing for an important, if oft-ignored, piece of cinema history. Hitch’ll leave you feeling in serious need of a shower, but you’ll also be haunted by the number of real-life witnesses who were unable to intervene. When lady-hate meets unchecked power, it’s way scarier than any horror film.